Workers, exposed to the danger of falling, often wear safety harnesses or belts. Typically, these safety devices are attached to a lifeline or lanyard. The lanyard, in turn, is securely affixed to a convenient anchorage point. Should the worker fall, his descent is quickly checked by the lanyard. Unfortunately, when the line has a great deal of slack (to accommodate worker movement), the worker may fall a considerable distance before the lanyard breaks his fall. Inasmuch as a falling body accelerates at a constant rate of 32 feet-sec.sup.-2 (9.8 meters-sec.sup.-2), the rapid deceleration of the falling worker caused by the sudden tautness in the lanyard may result in serious bodily injury. Indeed, it has been suggested that when a belt restraint system is utilized, the maximum force to be tolerated by a human being should not exceed 10 G forces. It should be appreciated, however, a falling person jerked to a stop by a suddenly rigid lanyard may experience forces considerably greater than 10 G's.
Accordingly, various shock absorbing or shock reducing systems for lanyards have been developed to absorb a substantial portion of the kinetic energy generated during a fall. In this manner, the worker is decelerated gradually rather than being brought to an abrupt halt. For example, systems employing elastic fibers, tear-away elements and piston-cylinder shock absorbers have been used to cushion the shock of a fall.
Under existing and proposed standards, lanyards which have been subjected to either impact loading by a falling worker or loading exceeding a predetermined value must be removed from service and replaced immediately. However, when a semi-drawn or bulked continuous filament fiber shock absorbing lanyard is employed, oftentimes it is difficult to determine whether the aforementioned conditions have indeed occurred. After one incident, such lanyards have outlived their usefulness. Clearly, a means of alerting an unsuspecting worker of the existing conditions of the lanyard is desirable and, in fact, necessary.